The present invention relates to a device for the metered passage of a liquid, comprising a container for the liquid, which is provided with an inlet and an outlet for supplying liquid to and discharging liquid from the container, respectively, and with a bottom and upright side walls joining said bottom, as well as metering means for regulating the extent to which liquid is supplied to the container via the inlet in dependence on the amount of liquid that is present in the container, said metering means comprising a floating element which floats on the liquid in the container and which is rigidly connected to an overflow edge that can move up and down together with the floating element between a lowermost position and an uppermost position, over which overflow edge the liquid flows into the container at the location of the inlet.
At the time of the present invention mention is made, both on the Internet (www.pondflow.com) and in advertisements, of a mechanical filter system known by the trade names PondSieve® and PondFlow®, with reference being made to patent (application) numbers 102279 as well as 1022779. Said system makes use of a reservoir in which a screen bend is disposed. A liquid, such as pond water, is supplied to the reservoir via a supply pipe that opens into the bottom of a separate container fitted with an overflow edge. Liquid that flows over said overflow edge falls on the screen bend, which cleans the liquid in that parts that are too large remain behind on the upper side of the screen, from which they are discharged in downward direction. Under the screen bend, the reservoir is filled with liquid that has already passed the screen bend, which liquid is sucked in by a pump. A floating element floats on the liquid in the reservoir, which floating element is connected to the overflow edge via a rod, so that said container moves up and down in its entirety together with the floating element, depending on the level of the liquid in the lower part of the reservoir. In connection with said up-and-down movement of the container, which has a limited capacity, the supply pipe is provided with a flexible, bellows-like portion, whose length can be varied. The level of the container provided with the overflow edge will rise along with the liquid level in the reservoir, so that the amount of liquid that flows over the overflow edge will decrease, as a result of which the liquid level in the reservoir will fall again, providing that the pump will continue to discharge liquid from the reservoir, and more liquid will flow over the overflow edge again. In this way a self-regulating system has been created.